UNO - 4 small servos - not enough power?

Hey guys,

Newbie here. I searched a bit but couldn't find the answer.

I'm trying to use 4 servos with my UNO board.
I managed to get 2 servos going, but when I plug in the other two they all start twitching.

I assumed I needed extra power.
I have a 9v battery and an Arduino adapter for it. I plugged it in, and used the Vin pin instead of 5v. Didn't solve the problem.
What am I doing wrong?


Yes, Uno only has 500mA (USB) to 800mA (Vin) capacity.
9V battery only has 200-300mAH capacity, will not last long.
Get a stronger battery (like 4 AAs, 4 Cs) and power the servos seperately from the Uno. Connect the battery ground to the Uno ground.

Typical setup for powering a servo.